1. Field of the Invention
The present invention relates to a circuit board device and a printed wiring board.
2. Description of the Related Art
Circuit board devices equipped with semiconductor integrated circuits (referred to as IC chips) have been known in the art. Japanese Patent Application Laid-Open No. 2009-027140, for example, proposes a circuit board device designed to reduce electromagnetic interference (EMI) due to common mode noise generated from a power supply and a ground terminal of an IC chip. In such a circuit board device, a power supply terminal and the ground terminal of the IC chip are connected to a conductor pattern through capacitors. There is described that, the conductor pattern is connected to a plane conductor connected neither to a ground plane nor to a power supply plane through a filter, thereby such a configuration relatively reduces common mode noise flowing through the power supply and the ground of a printed wiring board to be an antenna in the Japanese Patent Application Laid-Open No. 2009-027140.
Japanese Patent Application Laid-Open No. 2001-203434 proposes a printed wiring board designed to suppress unwanted electromagnetic radiation generated from circuit patterns formed in a power supply layer and a ground layer. Such unwanted electromagnetic radiation is similar to the EMI in Japanese Patent Application Laid-Open No. 2009-027140. Japanese Patent Application Laid-Open No. 2001-203434 describes that unwanted electromagnetic radiation can be suppressed by connecting a bypass capacitor having a resonant frequency approximately the same as a resonant frequency f of the printed wiring board itself equipped with no electronic components such as IC chips between the power supply layer and the ground layer of the printed wiring board.